CN110927122A - Phase type SPR detection device and method based on interference spectrum - Google Patents
Phase type SPR detection device and method based on interference spectrum Download PDFInfo
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Abstract
The invention provides a phase type SPR detection device and method based on interference spectrum, the device comprises: the device comprises a light source, a polarizer, a wave plate, an SPR sensing module, a spectrometer and a control terminal. The invention utilizes the wave plate with a certain thickness to generate phase delay for P polarized light and S polarized light in incident light, thereby generating a spectrum interference phenomenon; the frequency domain-time domain combined algorithm is carried out on the interference spectrum to analyze the SPR resonance wavelength and phase in real time, so that the SPR phase extraction accuracy is improved; the method comprises the steps of obtaining resonance wavelengths of samples with different refractive indexes, obtaining effective interference spectrums through the resonance wavelengths, further extracting SPR phase change from the effective interference spectrums, obtaining detection results of samples to be detected according to the SPR phase change, achieving SPR phase detection with a large dynamic range without any modulator compared with the traditional phase modulation SPR technology, and having the advantages of being strong in anti-noise capacity and low in research and development cost.
Description
Technical Field
The invention belongs to the technical field of optical sensing imaging, and particularly relates to a phase type SPR detection device and method based on interference spectrum.
Background
The Surface Plasmon Resonance (SPR) sensing technology has the advantages of no mark, real-time monitoring, less sample consumption, high sensitivity and high-throughput detection, and is widely applied to the fields of environmental monitoring, food safety, genomics, proteomics and the like. SPR is an optical phenomenon in which light incident on some metal surfaces under specific conditions is totally reflected, evanescent waves of the incident light incident on the metal resonate with surface plasmon waves of the metal surfaces, the resonance conditions are related to optical parameters of the metal film surface, and different types of SPR sensors, such as intensity modulation, angle modulation, spectral modulation, and phase modulation, are generated by identifying different resonant optical parameters.
Phase modulation SPR sensing techniques have the highest sensitivity, typically 10, compared to other modulation types-7To 10-9Between RIUs, but phase modulation SPR inherently has a small dynamic detection range (typically 10 a)-4RIU) and high sensing film thickness error requirement (usually 1-2 nm), and limits the application of the film thickness error detection method in practical detection. In order to improve the dynamic range of the phase SPR, an SPR sensing technology combining angle modulation and phase modulation is proposed by the university of Chinese university in hong Kong, phase modulation is carried out on incident light at different angles through a phase modulator, the phase change of the SPR phase at different angles is extracted through an algorithm, the dynamic range is expanded, and experimental results show that the dynamic range of the technology reaches 0.06RIU, and the sensitivity is 2.2 multiplied by 10-7RIU. Currently, for most phase modulation SPR techniques, a modulator is introduced to modulate or demodulate incident or reflected light, for example: piezoelectric ceramics (PZT), liquid crystal modulators (LC), liquid crystal phase retarders (LCVR), etcBut results in complicated SPR sensor structures and also increases the cost of the instrument.
Therefore, the prior art is subject to further improvement.
Disclosure of Invention
In view of the above disadvantages in the prior art, an object of the present invention is to provide a phase SPR detection apparatus and method based on interference spectroscopy, which overcome the defects of the conventional phase SPR apparatus that the dynamic detection range is small, and the modulator needs to be introduced to modulate or demodulate the incident light or the reflected light, resulting in a complicated apparatus structure and high cost.
A first embodiment of the present disclosure is a phase SPR detection apparatus based on interference spectroscopy, including:
a light source for emitting broadband light;
a polarizer for receiving and polarizing the broadband light to obtain polarized light;
a wave plate for receiving the polarized light and introducing an additional phase difference to P-polarized light and S-polarized light in the polarized light to obtain polarized interference light;
the SPR sensing module is used for placing a sample to be detected, generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase and reflecting the polarized interference light with changed phase;
the spectrometer is used for collecting the polarized interference light with the changed phase to obtain an interference spectrum;
and the control terminal is used for extracting SPR phase change from the interference spectrum and obtaining a detection result of the sample to be detected according to the SPR phase change.
The phase type SPR detection device based on interference spectrum, wherein the SPR sensing module comprises: the device comprises a prism, a sensing chip and a flow cell;
the prism is used for receiving the polarized interference light and enabling the polarized interference light to generate total internal reflection at the prism interface;
the sensing chip is used for generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase;
the flow cell is used for placing a sample to be detected and enabling the sample to be detected to pass through the surface of the sensing chip.
The phase type SPR detection device based on the interference spectrum is characterized in that a collimating lens group, a coupling optical fiber and a first lens are further arranged between the light source and the polarizer;
the collimating lens group is used for collimating and focusing broadband light emitted by the light source;
the coupling optical fiber is positioned between the collimating lens group and the polarizer and is used for coupling the collimated and focused broadband light;
the first lens is positioned between the coupling optical fiber and the polarizer and is used for collimating the broadband light coupled by the coupling optical fiber.
The phase-type SPR detection device based on interference spectrum, wherein the polarization direction of the polarized light generated by the polarizer is 45 degrees to the optical axis direction of the wave plate.
The phase type SPR detection device based on the interference spectrum is characterized in that an analyzer is further arranged between the SPR sensing module and the spectrometer; the polarization direction of the analyzer is vertical to the polarization direction of the polarizer; the analyzer is used for receiving the polarized interference light with the changed phase reflected by the SPR sensing module so as to eliminate stray light in the polarized interference light with the changed phase.
The second embodiment disclosed by the invention is a phase-type SPR detection method based on interference spectrum, which comprises the following steps:
polarizing broadband light emitted by a light source to obtain polarized light;
introducing an additional phase difference to P polarized light and S polarized light in the polarized light to obtain polarized interference light;
enabling the polarized interference light and an SPR sensing module for placing a sample to be detected to generate plasma resonance to obtain polarized interference light with changed phase;
collecting the polarized interference light with the changed phase to obtain an interference spectrum;
and extracting SPR phase change from the interference spectrum, and obtaining a detection result of the sample to be detected according to the SPR phase change.
The phase-type SPR detection method based on an interference spectrum, wherein the step of extracting the SPR phase change from the interference spectrum comprises:
carrying out window Fourier transform on the interference spectrum to obtain resonance wavelengths corresponding to samples with different refractive indexes;
determining effective interference spectrums corresponding to samples with different refractive indexes according to the resonance wavelength;
and extracting SPR phase changes corresponding to the samples with different refractive indexes from the effective interference spectrum.
The phase type SPR detection method based on the interference spectrum, wherein the step of performing window Fourier transform on the interference spectrum to obtain the resonance wavelengths corresponding to the samples with different refractive indexes comprises the following steps:
carrying out window Fourier transform on the interference spectrum to obtain a wavelength-phase change curve;
carrying out derivation on the wavelength-phase change curve to obtain a wavelength-phase change rate curve;
and obtaining the resonance wavelengths corresponding to the samples with different refractive indexes according to the wavelength-phase change rate curve.
The phase type SPR detection method based on the interference spectrum, wherein the step of determining the effective interference spectrum corresponding to the samples with different refractive indexes according to the resonance wavelength comprises the following steps:
carrying out SPR phase and wavelength detection on known samples with different refractive indexes to obtain a wavelength change value corresponding to a linear region with phase change;
and determining effective interference spectrums corresponding to the samples with different refractive indexes according to the resonance wavelength and the wavelength change value.
The phase-type SPR detection method based on the interference spectrum, wherein the step of extracting SPR phase changes corresponding to samples with different refractive indexes from the effective interference spectrum specifically comprises the following steps:
generating reference signals with different phases and different periods, and sequentially carrying out cross-correlation operation on the reference signals with different phases and different periods and the effective interference spectrum to obtain a two-dimensional array of correlation coefficients;
and acquiring SPR phase changes corresponding to samples with different refractive indexes according to the two-dimensional array of the correlation coefficients.
The phase type SPR detection device and method based on interference spectrum have the advantages that the wave plate with a certain thickness is used for generating phase delay on P polarized light and S polarized light in incident light, so that spectrum interference phenomenon occurs; the frequency domain-time domain combined algorithm is carried out on the interference spectrum to analyze the SPR resonance wavelength and phase in real time, so that the SPR phase extraction accuracy is improved; through the resonance wavelength that obtains different refracting index samples, obtain effective interference spectrum through resonance wavelength, and then extract SPR phase change from effective interference spectrum, and according to SPR phase change obtains the testing result of the sample that awaits measuring, compares in traditional phase modulation SPR technique, has effectively increased the detection dynamic range, does not need any modulator moreover, has the advantage that noise immunity is strong, research and development cost is low.
Drawings
FIG. 1 is a schematic structural diagram of an interference spectrum-based phase-type SPR detection apparatus provided by the present invention;
FIG. 2 is an interference spectrum recorded by a spectrometer in the interference spectrum based phase SPR detection apparatus of the present invention;
FIG. 3 is a graph of phase change rate versus wavelength for an interference spectrum obtained based on a windowed Fourier transform of the interference spectrum of the present invention;
FIG. 4 is a flow chart of a preferred embodiment of the method for detecting phase SPR based on interference spectroscopy provided by the present invention;
FIG. 5 is a graph of the effective interference spectrum of samples of different refractive indexes according to the resonant wavelength and the wavelength variation value in the present invention;
FIG. 6 is a comparison graph of phase errors calculated by the existing NCC algorithm and the IPSCC algorithm provided by the present invention in different periods;
FIG. 7 is a 3D diagram of correlation coefficient with phase and period variation obtained by cross-correlation operation of a reference signal and an effective interference spectrum in the present invention;
FIG. 8 is a graph showing the variation of phase with refractive index of samples of different refractive indices according to the phase SPR detection method based on interference spectroscopy provided by the present invention;
FIG. 9 is a superimposed graph of the linear regions of phase change corresponding to samples of different refractive indices obtained by the phase-type SPR detection method based on interference spectroscopy provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Existing phase modulation SPR devices have a small dynamic range and require the introduction of a modulator to modulate or demodulate incident or reflected light, such as: piezoelectric ceramics (PZT), liquid crystal modulators (LC), liquid crystal phase retarders (LCVR), etc., which not only result in a complicated SPR sensor structure, but also increase the cost of the instrument. In order to solve the above problems, the present invention provides a phase-type SPR detection apparatus based on interference spectroscopy, as shown in fig. 1. The apparatus of the present invention comprises: a light source 11 for emitting broadband light; a polarizer 15 for receiving and polarizing the broadband light to obtain polarized light; a wave plate 16 for receiving the polarized light and introducing an additional phase difference to P-polarized light and S-polarized light in the polarized light to obtain polarized interference light; the SPR sensing module 17 is used for placing a sample to be detected, generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase and reflecting the polarized interference light with changed phase; a spectrometer 20 for collecting the polarized interference light with changed phase to obtain an interference spectrum, and a control terminal (not shown in the figure) for extracting the SPR phase change from the interference spectrum and obtaining a detection result of the sample to be detected according to the SPR phase change. In the specific SPR detection process, broadband light generated by a light source is polarized through a polarizer 15 to obtain polarized light, and additional phase difference is introduced into P polarized light and S polarized light in the polarized light through a wave plate 16 to obtain polarized interference light; the polarized interference light is reflected by the SPR sensing model 17 with the sample to be detected, then the polarized interference light with the changed phase is obtained, the interference spectrum is obtained through the spectrometer 20, and the SPR phase change corresponding to the sample with different refractive indexes is obtained according to the interference spectrum, so that the sample to be detected is detected, and the whole SPR detection device does not need to modulate the light beam by using a modulator.
The SPR sensing block 17 includes: prism 171, sensing chip 172 and flow cell 173. The prism 171 is used for receiving the polarized interference light generated by the wave plate 16 and making the polarized interference light undergo total internal reflection at the interface of the prism 171; the sensing chip 172 is used for generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase; the flow cell 173 is used for placing a sample to be measured and allowing the sample to be measured to pass through the surface of the sensing chip 172. In practical applications, the sensing chip 172 is usually formed by a chemically stable gold film and probe molecules fixed on the surface of the gold film, plasma resonance is generated between the gold film and the polarized interference light, and the refractive index of the surface of the gold film is changed due to the combination of the probe molecules on the gold film and the sample to be detected, so that the phase of the reflected polarized interference light is changed to perform SPR detection on the sample to be detected. However, the light directly irradiates to the surface of the gold film from the air and can not excite the surface plasma wave, and the free electrons on the surface of the gold film can be excited to generate the surface plasma wave by utilizing the evanescent wave when the light generates total internal reflection at the glass interface. When the interaction between the molecules of the sample to be detected needs to be measured by the SPR detection apparatus, the sample to be detected flows in from one end of the flow cell 173, flows out from the other end of the flow cell 173 after passing through the sensor chip 172 (as shown by an arrow in fig. 1), and combines with the probe molecules on the sensor chip 172, so that the refractive index of the surface of the gold film on the sensor chip 172 changes, and further the phase of the polarized interference light reflected by the prism 171 changes, and therefore, the sample to be detected can be accurately detected by analyzing the phase of the polarized interference light reflected by the prism 171.
In a specific embodiment, the polarization direction of the polarized light generated by the polarizer 15 is 45 ° to the optical axis direction of the wave plate 16, so that the incident intensities of the P-polarized light and the S-polarized light are equal, and a good sinusoidal interference spectrum signal is ensured. Because the interference spectrum reflected by the SPR sensing module 17 needs to be analyzed to obtain the SPR phase change, the spectrum emitted by the light source 11 is a continuous broadband light, the light source 11 may be a halogen lamp, a white laser, or other related light sources, but a coherent light source such as a white laser may cause detection noise due to a speckle phenomenon, and thus the sensitivity of the system is affected. In one embodiment, the light source 11 is a halogen lamp.
In a specific embodiment, a collimating lens group 12, a coupling fiber 13, and a first lens 14 are further disposed between the light source 11 and the polarizer 15. The collimating lens group 12 is used for collimating and focusing the broadband light emitted by the light source 11, and includes a first lens 121 and a second lens 122. A coupling optical fiber 13 is further disposed between the collimating lens group 12 and the polarizer 15, and the coupling optical fiber 13 is configured to couple the collimated and focused broadband light. A first lens 14 is further disposed between the coupling fiber 13 and the polarizer 15, an exit end of the coupling fiber 13 is located on a focal plane of the first lens 14, and the first lens 14 is used for collecting and collimating the broadband light coupled by the coupling fiber 13. In the specific SPR detection process, broadband light emitted from a light source 11 is collimated and focused by a collimating lens group 12 to a coupling fiber 13 for coupling, and then is collected and collimated by a first lens 14 and then is irradiated onto a polarizer 15 for polarization.
In one embodiment, an analyzer 18 is disposed between the SPR sensing module 17 and the spectrometer 20. The polarization direction of the analyzer 18 is perpendicular to the polarization direction of the polarizer 15, and the analyzer 18 is configured to receive the polarization interference light with the changed phase reflected by the SPR sensing module 17, so as to eliminate stray light in the polarization interference light and improve the signal-to-noise ratio. A second lens 19 is further disposed between the analyzer 18 and the spectrometer 20, and the second lens 19 is configured to collect the polarized interference light after being analyzed by the analyzer 18.
In one embodiment, the polarized interference light collected by the second lens 19 enters the spectrometer 20, and the spectrometer 20 records the SPR polarized interference spectrum signal, and the interference spectrum obtained is shown in fig. 2. The method comprises the steps of carrying out window Fourier transform analysis on an obtained interference spectrum to obtain resonance wavelengths corresponding to samples with different refractive indexes as shown in figure 3, determining effective interference spectra corresponding to the samples with different refractive indexes according to the resonance wavelengths, extracting SPR phase changes corresponding to the samples with different refractive indexes from the effective interference spectra by utilizing a cycle iterative parameter scanning correlation operation (IPSCC algorithm), flexibly obtaining the resonance wavelengths aiming at the samples with different refractive indexes, obtaining the effective interference spectra corresponding to the samples with different refractive indexes by utilizing the resonance wavelengths, and effectively increasing a detection dynamic range without an external modulator compared with the traditional SPR technology.
In an embodiment, the present invention further provides an interference spectrum-based phase SPR detection method corresponding to the interference spectrum-based phase SPR detection apparatus described above, as shown in fig. 4, the method includes the following steps:
s1, polarizing the broadband light emitted by the light source to obtain polarized light;
s2, introducing additional phase difference to P polarized light and S polarized light in the polarized light to obtain polarized interference light;
s3, enabling the polarized interference light and an SPR sensing module for placing a sample to be detected to generate plasma resonance to obtain polarized interference light with changed phase;
s4, collecting the polarized interference light with changed phase to obtain an interference spectrum;
and S5, extracting SPR phase change from the interference spectrum, and obtaining a detection result of the sample to be detected according to the SPR phase change.
In a specific embodiment, in order to perform SPR detection on a sample to be detected, after a light source emits broadband light with continuous spectrum, the broadband light is polarized to obtain polarized light; introducing an additional phase difference to P polarized light and S polarized light in the polarized light to obtain polarized interference light; then the polarized interference light and an SPR sensing module which is placed with a sample to be detected generate plasma resonance, specifically, the polarized interference light and a sensing chip in the SPR sensing module generate plasma resonance, and the contact between the sample to be detected and the sensing chip can cause the refractive index change of the surface of the sensing chip, so that the phase change of the polarized interference light reflected by the SPR sensing module is caused, and the polarized interference light with the changed phase is obtained; and obtaining an interference spectrum by collecting the polarized interference light with the changed phase reflected by the SPR sensing module. The SPR phase change of the polarization interference spectrum caused by the combination of the sample to be detected and the sensing chip is extracted from the interference spectrum, so that the sample to be detected can be accurately measured, and the SPR phase change of the sample with different refractive indexes can be acquired, so that the SPR phase detection with a large dynamic range can be realized without an external modulator.
In one embodiment, step S5 specifically includes:
s51, carrying out window Fourier transform on the interference spectrum to obtain resonance wavelengths corresponding to samples with different refractive indexes;
s52, determining effective interference spectrums corresponding to samples with different refractive indexes according to the resonance wavelength;
and S53, extracting SPR phase changes corresponding to the samples with different refractive indexes from the effective interference spectrum.
In a specific embodiment, after obtaining the interference spectrum, performing window fourier transform analysis on the interference spectrum to obtain the resonant wavelengths of the samples with different refractive indexes; and then determining effective interference spectrums corresponding to the samples with different refractive indexes according to the resonance wavelengths of the samples with different refractive indexes, and extracting SPR phase changes corresponding to the samples with different refractive indexes from the effective interference spectrums. In a specific application process, a sample to be detected is combined with a sensing chip to cause the change of the surface refractive index of the sensing chip, the sensing chips with different surface refractive indexes correspond to different resonance wavelengths, effective interference spectrums corresponding to the samples with different refractive indexes are extracted from the resonance wavelengths, SPR phase changes corresponding to the samples with different refractive indexes are extracted from the effective interference spectrums by utilizing a related algorithm, and therefore the sample to be detected is detected.
In a specific embodiment, the step S51 specifically includes:
s511, performing window Fourier transform on the interference spectrum to obtain a wavelength-phase change curve;
s512, deriving the wavelength-phase change curve to obtain a wavelength-phase change rate curve;
and S513, obtaining the resonance wavelengths corresponding to the samples with different refractive indexes according to the wavelength-phase change rate curve.
In a specific embodiment, after obtaining the interference spectrum, first performing a window fourier transform on the interference spectrum to obtain a wavelength-phase variation curve; then, deriving the obtained wavelength-phase change curve to obtain a wavelength-phase change rate curve, and obtaining the wavelength corresponding to the maximum phase change rate from the wavelength-phase change rate curve, which is the resonance wavelength corresponding to the sample with different refractive indexes, as shown in fig. 3, the refractive index is n0And n1The refractive index n can be obtained from FIG. 3 by plotting the wavelength-phase change rate curve corresponding to the sample of (2)0Corresponding to a resonance wavelength of λ0Refractive index of n1Corresponding to a resonance wavelength of λ1。
In a specific embodiment, the step S52 specifically includes:
s521, SPR phase and wavelength detection is carried out on samples with different known refractive indexes, and a wavelength change value corresponding to a linear region of phase change is obtained;
and S522, determining effective interference spectrums corresponding to the samples with different refractive indexes according to the resonance wavelength and the wavelength change value.
In one embodiment, in order to obtain effective interference spectra corresponding to samples with different refractive indexes, SPR phase and wavelength detection needs to be performed on known samples with different refractive indexes in advance, and a wavelength variation value corresponding to a linear region of phase variation is obtained. During the specific experiment, the SPR phase detection and the SPR wavelength detection can be sequentially carried out on the samples with different refractive indexes by known samples with different refractive indexes, such as saline water with different concentrations. Acquiring the known SPR phase change and SPR wavelength change caused by samples with different refractive indexes, drawing a refractive index-wavelength curve and a refractive index phase curve, and reading an SPR wavelength range corresponding to a phase linear region, namely a wavelength change value corresponding to a linear region with phase change.
In one embodiment, assuming that the wavelength variation value corresponding to the linear region of the phase variation calibrated by the experiment is Δ λ, the resonance wavelength corresponding to the samples with different refractive indexes obtained in the previous step is λiAccording to the wavelength variation value Delta lambda and the resonance wavelength lambda corresponding to the samples with different refractive indexesiAnd determining the wavelength range of the effective interference spectrum, and determining the effective interference spectrum corresponding to the samples with different refractive indexes according to the determined wavelength range of the effective interference spectrum. The wavelength range of the specific effective interference spectrum is
When the refractive index of the sample changes, the interference spectrum also correspondingly moves, and the resonant wavelength of the sample is always positioned
Within the range when the resonant wavelength of the sample is out of
Within range, a new effective interference spectral range is selected, e.g.
Refractive index n0And n1The corresponding effective interference spectrum of the sample of (2) is shown in fig. 5.
In a specific embodiment, the step S53 specifically includes:
s531, generating reference signals with different phases and different periods, and performing cross-correlation operation on the reference signals with different phases and different periods and the effective interference spectrum in sequence to obtain a two-dimensional array of correlation coefficients;
and S532, acquiring SPR phase changes corresponding to the samples with different refractive indexes according to the two-dimensional array of the correlation coefficients.
In a specific embodiment, an existing correlation algorithm, such as an NCC algorithm, can obtain phase information of a sinusoidal signal, but during actual testing, a period of an actual signal often cannot be consistent with a reference signal, and a conventional correlation algorithm is susceptible to the influence of the period because the period of the reference signal is fixed, as shown in fig. 6, a calculation error of the existing NCC algorithm is larger due to the difference of the periods, and the larger the difference between the periods of the actual signal and the periodic signal is, the larger the calculation error of the phase is. The present invention proposes a parametric scan correlation algorithm (IPSCC algorithm) for extracting the SPR phase of the effective interference spectrum. The specific process is to generate reference signals with different phases and different periods:
n, M is 0,1,2,3 …, Δ N is the refractive index difference of the fast and slow axes of the wave plate, d is the thickness of the wave plate, φ is SPR phase, λ0For the initial wavelength of the resonance, the wavelength of the resonance,
is the initial phase. Then, the phase and the period of the reference signals are changed in sequence, and the reference signals and actual signals, namely effective interference spectra, are subjected to cross-correlation operation in sequence to obtain a two-dimensional array of correlation coefficients; and the phase corresponding to the reference signal with the maximum correlation number in the two-dimensional array of the correlation coefficients is the phase corresponding to the effective interference spectrum, and the SPR phase change corresponding to the samples with different refractive indexes is obtained according to the phase corresponding to the effective interference spectrum. In the specific implementation process, the reference signal is automatically generated by the software module, the phase of the reference signal changes with the change of N, the period changes with the change of M, the steps of sequentially changing the phase and the period of the reference signal are that N changes with one value, and M scans for one period, namely M gradually changes from 0 to +/-0.5 lambda0Or N scans for a period each time M changes by one value,/Δ λ, i.e. N changes stepwise from 0
Taking the actual measurement signal with the period of 1T and the SPR phase of 180 degrees as an example, a 3D graph of the correlation coefficient changing with the phase and the period is shown in FIG. 7As shown, the period and phase of the corresponding actual signal are 1T and 180 degrees, respectively, when the correlation coefficient is maximum (| R | ═ 1).
In one embodiment, as shown in FIGS. 8 and 9, the sample refractive index is assumed to be from n0Change to n1The spectrometer separately obtains the refractive index n0And refractive index n1Corresponding SPR interference spectrum, and obtaining refractive index n according to the interference spectrum0And refractive index n1Corresponding to resonance wavelength lambda0And λ1According to λ0And λ1Determining the corresponding effective interference spectrum, further obtaining the corresponding phase position through a parameter scanning correlation algorithm, and obtaining the phase position according to the refractive index n0And refractive index n1The corresponding phase obtains its phase variation
Similarly, a refractive index from n can be obtained1To n2Corresponding phase change
Refractive index from n2To n3Corresponding phase change
And from niTo ni+1Corresponding phase change
The total phase changes to
The first term in the formula is a low-precision measurement term based on the change of the resonance wavelength, and the second term is a high-precision phase measurement term.
In summary, the present invention provides an apparatus and a method for detecting phase-type SPR based on interference spectrum, the apparatus includes: a light source; a polarizer polarizing the broadband light emitted by the light source to obtain polarized light; a wave plate for introducing an additional phase difference to the P-polarized light and the S-polarized light in the polarized light to obtain polarized interference light; the SPR sensing module is used for placing a sample to be detected, generating plasma resonance with the polarized interference light, obtaining the polarized interference light with changed phase and reflecting the polarized interference light; the spectrometer is used for collecting the polarized interference light with changed phase to obtain an interference spectrum; and the control terminal is used for extracting SPR phase change from the interference spectrum and obtaining a detection result of the sample to be detected according to the SPR phase change. The invention utilizes the wave plate with a certain thickness to generate phase delay for P polarized light and S polarized light of incident light, thereby generating a spectrum interference phenomenon; the frequency domain-time domain combined algorithm is carried out on the interference spectrum to analyze the SPR resonance wavelength and phase in real time, so that the SPR phase extraction accuracy is improved; the method comprises the steps of obtaining resonance wavelengths of samples with different refractive indexes, obtaining effective interference spectrums through the resonance wavelengths, further extracting SPR phases from the effective interference spectrums, obtaining detection results of samples to be detected according to SPR phase changes, achieving SPR phase detection with a large dynamic range without any modulator compared with the traditional phase modulation SPR technology, and having the advantages of being strong in anti-noise capacity and low in research and development cost.
It is to be understood that the system of the present invention is not limited to the above examples, and that modifications and variations may be made by one of ordinary skill in the art in light of the above teachings, and all such modifications and variations are intended to fall within the scope of the appended claims.
Claims (10)
1. A phase type SPR detection apparatus based on interference spectrum, comprising:
a light source for emitting broadband light;
a polarizer for receiving and polarizing the broadband light to obtain polarized light;
a wave plate for receiving the polarized light and introducing an additional phase difference to P-polarized light and S-polarized light in the polarized light to obtain polarized interference light;
the SPR sensing module is used for placing a sample to be detected, generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase and reflecting the polarized interference light with changed phase;
the spectrometer is used for collecting the polarized interference light with the changed phase to obtain an interference spectrum;
and the control terminal is used for extracting SPR phase change from the interference spectrum and obtaining a detection result of the sample to be detected according to the SPR phase change.
2. A phase-type SPR detection apparatus according to claim 1, wherein said SPR sensing module comprises: the device comprises a prism, a sensing chip and a flow cell;
the prism is used for receiving the polarized interference light and enabling the polarized interference light to generate total internal reflection at the prism interface;
the sensing chip is used for generating plasma resonance with the polarized interference light to obtain polarized interference light with changed phase;
the flow cell is used for placing a sample to be detected and enabling the sample to be detected to pass through the surface of the sensing chip.
3. A phase-type SPR detection apparatus according to claim 1, wherein a collimating lens group, a coupling optical fiber and a first lens are further disposed between said light source and said polarizer;
the collimating lens group is used for collimating and focusing broadband light emitted by the light source;
the coupling optical fiber is positioned between the collimating lens group and the polarizer and is used for coupling the collimated and focused broadband light;
the first lens is positioned between the coupling optical fiber and the polarizer and is used for collimating the broadband light coupled by the coupling optical fiber.
4. A phase SPR detection apparatus according to claim 1 wherein the polarisation of the polarised light produced by said polariser is at 45 ° to the optical axis of said waveplate.
5. A phase-type SPR detection apparatus according to claim 1, wherein an analyzer is further provided between the SPR sensing module and the spectrometer; the polarization direction of the analyzer is vertical to the polarization direction of the polarizer; the analyzer is used for receiving the polarized interference light with the changed phase reflected by the SPR sensing module so as to eliminate stray light in the polarized interference light with the changed phase.
6. A phase type SPR detection method based on interference spectrum is characterized by comprising the following steps:
polarizing broadband light emitted by a light source to obtain polarized light;
introducing an additional phase difference to P polarized light and S polarized light in the polarized light to obtain polarized interference light;
enabling the polarized interference light and an SPR sensing module for placing a sample to be detected to generate plasma resonance to obtain polarized interference light with changed phase;
collecting the polarized interference light with the changed phase to obtain an interference spectrum;
and extracting SPR phase change from the interference spectrum, and obtaining a detection result of the sample to be detected according to the SPR phase change.
7. The interference spectrum-based phase SPR detection method of claim 6 wherein said step of extracting SPR phase changes from said interference spectrum comprises:
carrying out window Fourier transform on the interference spectrum to obtain resonance wavelengths corresponding to samples with different refractive indexes;
determining effective interference spectrums corresponding to samples with different refractive indexes according to the resonance wavelength;
and extracting SPR phase changes corresponding to the samples with different refractive indexes from the effective interference spectrum.
8. The method for phase SPR detection based on interference spectrum of claim 7, wherein said step of performing a windowed Fourier transform on said interference spectrum to obtain resonance wavelengths corresponding to samples with different refractive indexes comprises:
carrying out window Fourier transform on the interference spectrum to obtain a wavelength-phase change curve;
carrying out derivation on the wavelength-phase change curve to obtain a wavelength-phase change rate curve;
and obtaining the resonance wavelengths corresponding to the samples with different refractive indexes according to the wavelength-phase change rate curve.
9. A phase SPR detection method according to claim 7 wherein said step of determining the effective interference spectra for samples of different refractive index according to said resonance wavelength comprises:
carrying out SPR phase and wavelength detection on known samples with different refractive indexes to obtain a wavelength change value corresponding to a linear region with phase change;
and determining effective interference spectrums corresponding to the samples with different refractive indexes according to the resonance wavelength and the wavelength change value.
10. The method for phase SPR detection based on interference spectroscopy of claim 7, wherein said step of extracting SPR phase changes corresponding to samples with different refractive indexes from said effective interference spectrum specifically comprises:
generating reference signals with different phases and different periods, and sequentially carrying out cross-correlation operation on the reference signals with different phases and different periods and the effective interference spectrum to obtain a two-dimensional array of correlation coefficients;
and acquiring SPR phase changes corresponding to samples with different refractive indexes according to the two-dimensional array of the correlation coefficients.
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